To practically obtain this result in cast-iron guns, Rodman had them cast on a hollow core and cooled from within by passing a stream of water through them. In 1850 Admiral Dahlgren proposed a new system of cast-iron guns for the navy, which upon trial gave very favorable results and was adopted in 1855. His guns (9, 10, and 11-inch) were made of cast iron, solid, and cooled from the exterior; to obviate the difficulty of strain due to unequal shrinkage, they were cast nearly cylindrical and then turned down to the required shape, thus getting rid of the exterior metal which caused the strain by cooling first in the mould. The chamber is of the Gomer form, the thickness of the metal around the seat of the charge being a little greater than the diameter of the bore; the chase tapers more rapidly than in other cast-iron guns, which makes the breech appear thicker than it really is. In 1857 the calibres of the land service consisted of 10 and 8-inch columbiads, 42, 32, 24, 18, and 12-pdr. guns, 10 and 8-inch and 24-pdr. howitzers, and 13, 10, and 8-inch mortars, all of cast iron.

Besides the light 12-pdr. or Napoleon gun, the bronze pieces consisted of heavy 12 and 6-pdr. guns, and of 32, 24, and 12-pdr. howitzers, together with 12-pdr. mountain howitzers and 24-pdr. Coehorn mortars. - We have now come to the most recent period in the history of artillery improvement, extending from the Italian campaign of 1859 to the present date (1873). Although the employment of rifle cannon in war was originally attempted by the English, the French are entitled to the credit of first successfully using them in battle. The English 68-pdr. and 8-inch Lancaster rifles failed at Sebastopol in 1854, the shot jamming in the bores; but the French bronze rifled fours, after a model devised by Col. Treuille de Beauheu, were brilliantly successful in the Italian campaign of 1859. So recent was their construction that the batteries had to march with empty carriages, the guns being boxed up and sent to the army after it had left France. Once in Italy, the incontestable superiority of the French artillery seemed to recall the days of Charles VIII.; at Solferino particularly, it destroyed the Austrian batteries at the unprecedented range of 1,600 yards before they could get into position to return the fire, and shook the confidence of the reserves by shelling them at distances hitherto deemed entirely safe. • When every gun fired a cast-iron spherical projectile, its weight indicated the diameter of the bore, or calibre of the piece; but with the elongated projectiles of rifled cannon which are of various lengths, the case is very different, the weight of the shot being no indication of the power of the gun, nor giving any definite idea of the size of the bore.

With French rifle projectiles whose length does not exceed twice their diameter, the same numbers designate their calibres as of old, but they now refer to kilogrammes instead of pounds; thus the 4-pdr., or four, formerly meant that the gun fired a cast-iron sphere weighing 4 lbs., but now signifies that its projectile weighs about 4 kilogrammes or 8.823 lbs. Compared with English guns of the same diameter of bore, the French throw a lighter shot, the English projectiles, particularly the Whitworth, being always longer. The rifled twelves, consisting of the gun-howitzers (Napoleon guns) converted by rifling, were not used in Italy, there not being enough ammunition, but were successfully tested in Mexico; at Puebla they were found very useful in breaching masonry. The French also transformed by rifling the old 12-pdr. field gun into a gun of reserve and position, the old long 12-pdr. gun into a garrison gun, and the short 24-pdr. gun and 50-pdr. gun into siege guns. None of these pieces fire solid shot; the three kinds of twelves use the same projectiles, but with different charges of powder.

The short twenty-four weighs 2,000 kilogrammes or two tons, and the charge is varied according to the range desired, up to a maximum of 2 1/2 kilos (5 1/2 lbs.), which gives a range of 5,000 metres; the carriage of the gun enables it to be fired as a mortar. The long twenty-four only differs from the short by its length and weight, which is three quarters of a ton (740 kilos) more. The fifty is not heavier than the short twenty-four, and is fired with the same charge of powder; its projectile weighs 51 kilos (113 lbs.), with a bursting charge of 3.5 kilos (7 lbs. 13 oz.). Both are mounted on the same carriage, which is drawn by only six horses. Following the same principles, the French artillerists have also utilized some of the old Paixhans guns by rifling and hooping with steel; a gun of this kind of 22 centimetres bore weighs about 14 tons, and throws 170-lb. hollow projectiles to a distance of 6,000 or 7,000 yards. So, too, with their naval guns: the old thirties, originally intended to carry spherical 32-lb. shot with a charge of 11 lbs., after being hooped and rifled became useful and valuable pieces. ! Although the French artillery board rejected | the breech-loading system as a needless com- plication for field guns, they were quick to adopt it for heavy ordnance as economizing space, greatly increasing the ease and rapidity of loading, and affording more protection to the cannoneers.

The principal French naval guns are the 6 1/2-inch, 7 1/2-inch, 9 1/2-inch, and 10 3/4-inch breech-loading rifles, consisting of a core of cast iron with areenforce of steel hoops made of a double series of steel rings, one over the other, so as to break joints. In the aperture of the bore a female screw of 15 or 16 threads is cut into the metal of the gun, which receives a cylindrical screw or breech plug, mounted in front, with an elastic steel cup or gas check. That time may not be wasted at each discharge by screwing and unscrewing the whole length of the plug, its surface, as well as that of the female screw in the breech, is divided into six equal parts, from three of which the threads are removed; when the breech is to be closed the threaded portions of the plug are presented so that they come opposite the smooth parts of the hole, and vice versa; the plug or stopper is then pushed in, and a third of a turn with the handle brings the screws of both parts together. No further changes were made in the materiel of the field batteries before the war with Prussia in 1870, where the French guns for the first time in history were found far inferior to those of their opponents in range, accuracy, and power of execution, the weakest points about them being the want of flatness in the trajectory and the rapidity with which enlargements and lodgments occurred in the soft metal of the bore.